Luminescence of Cul Films and Its Correlation to the Exciton

Resonance emission in Cul fiilms has been obtained for the exciton generated by the optical transition from the valence band having the symmetry \(₈\) of zinc blende structure. The Stokes shift in thick films amounts to 20Å. The shift has been found to depend much upon the film thickness. With preparing the thin film of the wedge shape, the variation of the Stokes shift has been measured as a function of the film thickness. The shift is found to show the decrease as the film thickness becomes thinner than 1.1 µ. In a very thin film, there is no Stokes shift. Discussions are given for the variation of the shift in connection to the exciton diffusion.